1. Field of the Invention
This invention relates to light channels for indicating lights in computer systems and particularly to light channels that include electromagnetic interference (EMI) shielding.
2. Description of the Related Art
Many computer systems, including personal computers, workstations, servers, and embedded systems are designed to have multiple peripheral devices included in the system. A typical personal computer system includes a processor, associated memory and control logic and a number of peripheral devices that provide input and output (I/O) for the system. Such peripheral devices include, for example, compact disk read-only memory (CD-ROM) drives, hard disk drives, floppy disk drives, and other mass storage devices such as tape drives, compact disk recordable (CD-R) drives or digital video/versatile disk (DVD) drives. Additionally, computer systems often have the capability to interface with external enclosures that include additional peripheral devices.
Because these peripheral devices, and other portions of a computer system as well, often have one or more indicating lights, typically light emitting diodes (LEDs), the chassis or enclosure of the computer system is designed to allow the indicating lights to be seen by a user. This is typically accomplished using holes or slots in the chassis or enclosure that correspond with the position of the indicating lights. In computer systems that have a large number of closely spaced indicating lights, for example a server having multiple hard disk drives, each with multiple indicating lights, holes accommodating individual lights often overlap, making a single large slot preferable to several small holes. Although large slots accommodating multiple adjacent holes can be preferable from a manufacturing perspective, large openings in the computer system chassis can lead to electromagnetic interference (EMI) problems.
High speed electronic computer components inside the computer system chassis create radio frequency emissions that can interfere with other devices. Doors, removable panels, displays, ventilation openings, and other holes in the chassis allow unwanted EMI to escape the enclosure. In order to contain the EMI, openings in the chassis must be made as small as possible, or shielding must be provided to minimize the amount of EMI emanating from the chassis.
Additionally, when closely spaced indicating lights are not mounted flush with or protruding from the computer system chassis or enclosure (i.e. the lights are mounted some distance behind the front of the chassis) light from one indicating light is likely to bleed-over to an adjacent indicating light, making it difficult for a user to be certain whether one or both of the two lights are on or off. This problem can be compounded when there is some intervening layer that tends to diffuse the light from the indicating lights, such as, for example, a Mylar.RTM. label that adheres to the front of the computer system over the openings for the indicator lights and includes icons for labeling each light's function or purpose.
Accordingly, it is desirable to have a device that can shield some or all of the light from adjacent indicating lights and thereby prevent light bleed-over, while at the same time reducing the amount of EMI the escapes a computer system chassis or enclosure through holes or slots associated with the indicating lights.